Int. J. Intelligent Information and Database Systems, Vol. 12, No. 4, 2019 245 Copyright © 2019 Inderscience Enterprises Ltd. Query optimisation in real-time data warehouses Issam Hamdi* and Emna Bouazizi MIRACL Laboratory, University of Sfax, Sfax 3018, Tunisia Email: haamdiissam@gmail.com Email: emna.buazi@gmail.com *Corresponding author Jamel Feki Faculty of Computing and IT, University of Jeddah, Jeddah, Saudi Arabia and MIRACL Laboratory, University of Sfax, Sfax 3018, Tunisia Email: Jamelfei@gmail.com Abstract: A real-time data warehouse (RTDW) allows decision makers to analyse fresh data as fast as possible in order to support real-time decision processes. In this paper, we focus on optimisation techniques to speed up query processing; in particular, we propose a dynamic selection of materialised views algorithm (DynaSeV) which selects views from results of incoming queries. Secondly, we suggest a new update policy to dynamically maintain materialised views. In addition, we propose a novel data partitioning approach for RTDW, called 2LPA-RTDW (Two-Level data Partitioning Approach for RTDW) by allowing unbalance of data amount in each partition. Then, we present our architecture called DETL-(m, k)-firm-RTDW architecture (decentralised extract-transform-load approach based on (m, k)-Firm constraints for RTDW) which deals with diversity and disparities in data source systems to reduce the time for ETL. Finally, we evaluate our contributions using the TPC-DS (TPC, 2014) benchmark; the preliminary results are quite promising. Keywords: real-time data warehouse; RTDW; real-time transactions; materialised views; data partitioning; extract-transform-load; ETL. Reference to this paper should be made as follows: Hamdi, I., Bouazizi, E. and Feki, J. (2019) ‘Query optimisation in real-time data warehouses’, Int. J. Intelligent Information and Database Systems, Vol. 12, No. 4, pp.245–278. Biographical notes: Issam Hamdi is a PhD student at the Department of Computer Science of the Faculty of Economics and Management of Sfax, Tunisia. His researches are done in MIRACL Laboratory (Tunisia). He received his Masters in Computer Sciences from the University of Gabes, Tunisia in 2012. His research interests include quality of service, real-time data warehousing, and feedback control architecture.